The effects of acute and chronic myocardial ischemia produced by coronary artery occlusion on left ventricular (LV) dynamics will be studied in intact conscious dogs. Animals will be instrumented for measurement and radio telemetry of: 1) overall LV function with LV miniature pressure gauges for LV systolic and diastolic pressure, dP/dt and dP/dt/P and endocardial dimension transducers for LV diameter and dP/dt, i.e., velocity of myocardial fiber shortening and aortic electromagnetic flow probes for stroke volume and cardiac output; 2) regional LV function with multiple pairs of minature ultrasonic crystals implanted in the LV for regional segment length and regional velocity of myocardial fiber shortening along with a miniature LV pressure gauge; 3) regional blood flow with Dopper or electromagnetic flow transducers on the mesenteric, renal, iliac and non-occluded coronary arteries. All animals will have flow probes on either the left circumflex and/or anterior descending coronary arteries. Coronary blood flow will be reduced in the left main, left anterior descending or left circumflex coronary arteries by inflation of implanted hydraulic occluders. Overall LV function as well as function of specific regions, which may be normally perfused, ischemic or in the border zone, will then be correlated with a measure of regional myocardial blood flow determined by the microsphere technique.